These are my settings for running FT8 on Windows. Some of them are personal preference, but either way, it should help you get up and running.
IC-7300
RF POWER: 35%
MODE: USB-D
FILTER: FIL1 (3.6k)
P.AMP/ATT: (leave default)
AGC: FAST
NB: OFF
NR: OFF
USB MOD Level: 40%
DATA OFF MOD: MIC/ACC
DATA MOD: USB
USB Serial Function: CI-V
CI-V Baud Rate: Auto
CI-V Address: 94h
CI-V Transceive: ON
CI-V USB Port: Unlink from [REMOTE]
CI-V USB Baud Rate: 115200
CI-V USB Echo Back: ON
PTT Start: ON (except on 6m where tuner can’t be used with my MFJ-929)
WSJT-X
Baud Rate: 115200
Data Bits: 8
Stop Bits: 2
Handshake: None
PTT Method: CAT
Mode: Data/Pkt
Split Operation: Fake It
Windows
Set Windows audio playback device to 100%, disable all enhancements, and set default format to 1 channel, 48000 Hz.
Set Windows audio recording device so that the green RX bar in WSJT-X is around 30% on a quiet band/frequency. Set default format to 1 channel, 48000 Hz.
Label the audio devices as “IC-7300”.
When transmitting, adjust Pwr slider in WSJT-X until it begins to tickle the ALC meter. Forward power should now be around 28W.